Why can other animals impregnate humans?
Um, in theory chimps and humans could produce offspring, although probably not offspring capable of reproduction. Like mules, which are produced by breeding horses and donkeys. Humans and chimps are closer than horses and donkeys genetically. Obviously such a pairing would be highly unethical, and there is no record it ever occurred. Maybe….
The chromosomes simply won’t match up, among other incompatibilities. Technically, there were other species of hominids that might have been able to produce hybrid offspring with modern humans (like perhaps homo erectus, neanderthals, or even earlier ones) but they’re all now extinct. As for chimpanzees (are closest living relative), I believe cross-fertilization has already been attempted in the laboratory but no embryos developed so far. However, with a little genetic manipulation here and there it might work.
